X-ray screen for taking skiagrams



June 28 1927.

. R. MANNL x-nAY SCREEN Fon T Axm' sxncmuls mea .my s; 192s PatentedJune 28, 1927.

RUDOLF MANNL, 0F KARLSBAD, CZECHOSLOVAKIA.

X-BAY SCREEN FOR TAKING SKIAGRA'MS.

Application filed July 9, 1925, Serial No. 42,593, and in CzechoslovakiaJuly 11k, 1924.

The present invention relates to X-ray screens, and has tor its purposeto provide a screen in which small deviations from exact "adjustmentwill not, as in screens heretofore proposed, cause large shadowsto beapparent in the middle of the field of view. i

According to this invention the height of the plates ward themiddle oftlierscreen so that the plate-s are narrower in the middle than at theedges oi the screen. As a result, thescreeu can be used even when itscentering is not exact and this is oic importance when the screen isadjusted by hand only.

In the accompanying drawings:

Figure l is a somewhat diagrammatic perspective view oi' a screen ofwell known type.

Fig. 2 structed vention.

Fig. 3 is a perspective view and Fig. 4 a cross section or' the screenmounted with the associated elements with which it is used.

As can be seen from the well known screen oit Fig. l, the plates are ofunvarying height from the edges of the screen to its center.

is a similar view of a screen con# in accordance with .the present in-However, in accordance with the present invention (Fig. 2), the platesare more permeable at the middle of the screen to the primary X-rays;for example, the material from which the plates are made is render-edmore permeable to X-rays near to the middle of the screen by alteringits mass, thickness or composition. When such a screen is turned aboutits axis the plate shadows wholly disappear without the appearance otpoints or concentric circles. The center point may even become invisibleas, although the plates are spaced more closely together, they are moretransparent. The invention is also applicable to screens such forexample as spiral screens.

of an X-ray screen decreases to- The embedding material for the platesis,

1n another embodiment of this invention, so 45 selected that itspermeabilityl to X-rays is greater at the edges of the screen than atits middle point, which has also for effect to equalize the action ofthe screen at all portions. l c

A practical way of carrying out the invention is illustrated in Figs. 3and 4, where the screen is rovided with radial kplates l, each of whichias one edge sloped so as to be narrower at the middle of the sreen.Above the screenis placed a movable cover 2 permeable to X-rays andwhich is arched and pei'- mits the soft parts of the body illuminated tobe compressed. v

The screen is also provided with a. well known rotating devicecomprising a pinion secured to the shaft of motor 3 and engaging anannular gear on the screen.

I claim:

l. An X-ray screen having plates converg- 35 ing in a common point, saidplates being of decreasing height toward said point of convergence.

2. A screen as claimed in claim 1,in which the material of which theplates are made is of different quality at the center, so that theplates are more permeable near the middle of theield of view.

3. Ascreen as claimed in claim l, having embedding material for theplates, and in which the X-ray permeability of said ma-V terial isgreater at'the edges of the screen than at its middle point.

4. A screen as claimed in claim l, providedl with an arched protectingcover formed of so a material permeable to X-rays. f

In testimony whereof I have signed my name to this specification.

DR. RUDOLF MANNL.

